Periodic Mesoporous Materials for Overall Water Splitting: Design of an Artificial Leaf

The overall splitting of water to produce hydrogen and oxygen using visible light photocatalysts is considered to be a holy grail in chemistry. Several semiconductors have been developed towards this purpose, however despite intense research, they suffer from poor quantum efficiencies. Furthermore, the development of stable and robust visible light absorbing photocatalysts seems to pose greater challenges.

In recent years, periodic mesoporous have attracted attention as support materials for catalytic reactions. Among the various classes of M41S series of materials, the cubic form called MCM-48 is an attractive material compared because it’s three-dimensional interpenetrating network of pores that provides efficient diffusion of reactants and products to the photocatalytically active sites. In addition, MCM-48 mesoporous materials also have high surface areas, tunable pore sizes, and large pore volumes that facilitate good dispersion of catalytically active sites. Our results show that the cubic MCM-48 materials containing spatially isolated titania clusters are efficient photocatalysts compared to titania incorporated into one-dimensional mesoporous supports such as MCM-41. Our research has demonstrated that titanium dioxide and CdS quantum dots can be well-dispersed within the MCM-48 mesoporous matrix. By deposition of RuO₂ onto the CdS-Ti-MCM-48 photocatalyst, photocorrosion can be completely suppressed. The photocatalyst, RuO₂-CdS-Ti-MCM-48 is the first known visible light photocatalyst capable of overall water splitting.